1. Field of the invention
This invention relates in general to the hypodermic injection of medication and specifically to the hypodermic injection of a self contained prepackaged unit dose of medication through a needle with an integral needle guard. Intradermal injection is a subset of the category of hypodermic injections.
2. Description of related art
A common form of hypodermic injection of medication is the intradermal injection. Intradermal injection using a small syringe attached to a short, fine gauge needle placed just below the skin surface is an extremely common medical procedure. Most often this procedure is used to administer a very small dose of lidocaine to produce a skin wheal of local anesthetic before the introduction of a larger more painful needle or instrument through that area of skin. This is frequently done prior to the insertion of a larger bore intravenous catheter. About 110 million such catheters alone are used annually, most of which would be facilitated by the prior use of an intradermal anesthetic skin wheal. Another occasion when the intradermal anesthetic skin wheal is used is prior to the introduction of a needle for a diagnostic radiologic procedure such as the X-ray needle localization of a breast mass. There are many other diagnostic and therapeutic medical procedures which routinely require the prior use of the intradermal injection of local anesthetic medication.
Another common form of hypodermic injection of medication is a subcutaneous injection using a slightly longer, fine gauge needle placed in the subcutaneous tissue between the skin and muscle. This procedure is commonly used, for example, to administer a standard dose of heparin in the prophylaxis of phlebitis.
Ordinarily, when an intradermal anesthetic skin wheal or a subcutaneous injection is administered, the practitioner uses a 1 cc tuberculin or insulin syringe with a fine gauge needle. The syringe is, of course, a piston within a cylindrical chamber made of glass or plastic. The local anesthetic or other medication must first be drawn up from a multidose vial, the ubiquitous air bubble tapped to the top of the syringe and ejected, the skin wheal administered, and the used syringe dangerously recapped or, alternatively, set aside unguarded, to be disposed of later. Needle guards for hypodermic needles have consisted of separate caps whose use may increase the likelihood of needle stick injury. Other needle guards attached to a conventional injection device or syringe require a separate action for their deployment. The disadvantages of the above technique, using the conventional syringe and needle, are as follows:
1. Using only a small amount of medication from a large vial may not be cost effective due to waste. PA1 2. The multidose vial may be cross contaminated after frequent use and storage. PA1 3. The drawing up of medication is time consuming and inconvenient. PA1 4. The possibility exists of transmitting infection from inadvertent needle stick from the unguarded used needle.
The solution to the disadvantages above is to make available the proposed intradermal or hypodermic injection device, containing a prepackaged unit dose of medication, attached to a needle with an integral needle guard which is deployed by the same easy action by which the medication is administered.